Unquoted Keys

While this is not really data type, it is kind of convention
allowing to use unquoted keys in complex structures.

If constant exists named same as key, the constant value
will be used instead also be aware of self
or static keywords.

Having above warning in mind, it is better to quote keys
with single ' or double " quote . However most likely keys will
be lowercase and constant uppercase, it is up to
developer to use unquoted keys.